Portable communication device having back-lighting and high key press noise margin

A method of reading key presses and backlighting a mobile communication device, comprising:

• providing a main module having a call receiver and a call sender;
• providing a keyboard module resident on a flip module separate from the main module, wherein the keyboard module includes thereon a plurality of marked keys,
• backlighting the plurality of keys by at least one light;
• controlling, by a central processing unit, of activation of the at least one light;
• interconnecting the flip module and the main module using a two wire interface having a first voltage line and a second voltage line;
• receiving a first switch command from the CPU;
• switching to a first positive voltage between the first voltage line and the second voltage line according to said receiving the first switch command;
• reading of a pressed at least one of the plurality of keys by the central processing unit upon said switching to the first positive voltage;
• receiving a second switch command from the CPU;
• switching to a first negative voltage between the first voltage line and the second voltage line according to said receiving the second switch command;
• activating the at least one light upon said switching to the first negative voltage.

A mobile communication device, comprising:

• a main module having a call receiver and a call sender;
• a keyboard module resident on a flip module separate from said main module, wherein said keyboard module includes thereon a plurality of marked keys,
• means for backlighting the plurality of keys;
• means for controlling activation of said means for backlighting;
• means for interconnecting said flip module and said main module;
• means for switching that places a first positive voltage on said means for interconnecting to allow for a reading, by said main module, of a pressed at least one of the plurality of keys, and which places a first negative voltage on said means for interconnecting to prevent the reading, by said main module, of a pressed at least one of the plurality of keys.